Case fastenings



Dec. 5, 1967 J. LITTLE 3,356,245

CASE FASTENINGS Filed Oct. 24, 1965 2 Sheets-Sheet 1 E .2 y 9 j A 6 5 .5.

a 7 U I 594 5% j 7/ 5 U Zap/J 2? I) I I /7 7 Dec. 5, 1967 Filed 001:. 24, 1965 J. LITTLE CASE FASTENINGS 2 Sheets-Sheet United States Patent 3,356,245 CASE FASTENINGS John Little, Kingsthorpe, Northampton, England, assignor to Painton 8: Company Limited, Kingsthorpe, Northampton, England, a British company Filed Oct. 24, 1965, Ser. No. 504,315 Claims priority, application Great Britain, Oct. 30, 1964, 44,381/64 6 Claims. (Cl. 220-4) ABSTRACT OF THE DISCLOSURE The invention is concerned with securely attaching part-casings to one another to form a complete casing. The solution provided by the invention is the provision on the part-casings of projections which are rigidly strapped to one another by non-yielding clips. These clips, formed by metal washers, E-clips, perforated plates and the like, embrace the projections and are rigidly held flush against the side of the casing by them.

Various miniature electronic components are housed inside casings made of resinous plastics material which may be of thermo-setting type or thermo-plastics type. Such casings are generally made as two or more moulded part-casings which are fitted together and then fastened to one another by riveting, glueing or heat sealing their contiguous edges.

With the increasing tendency towards miniaturisation of components the casings for them have become progressively smaller and this has resulted in the conventional methods of fastening the part-casings together being not altogether satisfactory. When the casing is in the form of a thin-walled plastics box the use of rivets passing between opposite sides of the box is unsatisfactory as the rivet heads press down on the top and bottom faces of the casing. This pressure is transmitted to the side walls where the edges of adjacent part-casings fit together, and there is a likelihood of failure at this joint through one edge moving sideways away from the other edges. A thin-walled box also tends to yield excessively to the rivet pressure when made of plastics material and the control of rivet length makes it ditficult to have a constant rivet pressure. A further difiiculty experienced with rivets is that they pass through the casing and the components therein and therefore near to electrically live parts. Thus there is often a danger of electrical shorting between the live parts and the rivet occurring inside the casing, especially under damp conditions.

The use of glueing or heat sealing of the contiguous edges of the part-casings together is also not wholly satisfactory where the casings have thin Walls as the wall thickness is generally insuificient to give enough strength to a glued joint. Although heat-sealing of the edges of the part-casings could, theoretically provide a welded joint between the part-casings as strong as the wall of each, in practice this is seldom the case and to get a satisfactory joint by heat-sealing involves carefully controlled equipment and a relatively slow rate of production.

7 An object of this invention is the provision of an improved method of fastening together two part-casings to form a section of a casing or a whole casing.

' A second object of this invention is the provision of an easily opened casing for an electrical or electronic component.

A third object of this invention is the provision of a relatively thin plastics casing held together by metal locking elements.

A fourth object of this invention is the provision of easily applied means for simultaneously fastening together two or more part-casings to form a complete casing for an electrical or electronic component.

A fifth object of this invention is the provision of strong fastening fixtures for relatively weak casings made of thin plastics materials and of small size.

A sixth object of this invention is the provision of a fastening fixture for securing together in a manner which lends itself to mass-production, a plastics casing of small size for a miniature electronic or electrical component.

A seventh object of this invention is the provision of a fastening fixturewhich securely holds part-casings together but which may be readily dismantled to enable components mounted inside the casing to be inspected, and then re-assembled to fasten the part-casings together again.

An eighth object of this invention is the provision of a fastening fixture for holding together part-casings of an electrical component, such as the lid and body of a thin plastic casing, without danger of the thin part-casings being severely stressed by the fixture.

These and other objects of the invention will become apparent from the following description:

A component casing, in accordance with the present invention includes two moulded part-casings fitting together along a common division line and fastened to one another by fixtures projecting from the sides of the casing, each fixture including two projections integral with respective part-casings and held rigidly in relative positions by a locking element through which the two projections pass and which is held by them against the side of the casing.

The locking element may be held against the side of the casing by enlargements formed on the two projections, such enlargements being conveniently made when the projections are formed of a thermo-plastics material by applying heat and pressure to the projections so that some of the thermo-plastics material is caused to flow and harden as a flange around an aperture in the locking element through which the projections extend. The locking element may be provided with a separate aperture for each of the two projections and in this case the locking element suitably comprises a flat metal plate. Alternatively the two projections of each fixture may pass through the same aperture in the locking element and in this case the locking element may comprise a washer, circlet or thin metal band.

In an alternative form of the invention the locking element is made of a strong resilient material, such as metal, and is sprung onto the two projections. In this arrangement the projections may be moulded of a relatively hard thermo-setting material. The locking element is conveniently provided with teeth which bite into the projections when the locking element is sprung onto them so that the locking element cannot be dislodged except with a tool especially made for the purpose. The advantage of this arrangement is that the locking elements of the casing may be removed to allow the two partcas-ings to be separated so that the electrical components mounted inside the casing can be inspected and replaced if necessary. The locking element can then be sprung back into position onto the two projections when the two part-casings are again fitted together. In the preferred arrangement the two projections associated with respective part-casings together form a cylindrical stud onto which the locking element is sprung. Each projection may be of semi-circular cross section providing a diametric face lying in the same plane as the common division line between the two part-casings.

In carrying out the invention the two part-casings preferably fit together with a spigot and socket connection, the spigot being provided around the rim of one partcasing and the socket being provided around the rim of the other part-casing.

The invention is usable for fastening together several part-casings which together form the casing of a component. The preferred method of fastening a plurality of part-casings together side-by-side is by using a locking element in the form of a plate which spans the adjacent sides of respective part-casings and is provided with apertures for receiving projections extending from the partcasings respectively. Such a technique is particularly useful for fastening rigidly together a number of identical subassemblies such as are sometimes used to build up a multiple electrical connector.

The invention will now be described in more detail, by way of examples with reference to the accompanying drawings, in which:

FIGURE 1 is a perspective view of a potentiometer casing in accordance with the invention;

FIGURE 2 is a section through part of FIGURE 1 and taken on the line and in the direction indicated by arrows IIII in that figure;

FIGURE 3 shows, in plan a spring metal washer;

FIGURE 4 is a view, corresponding to FIGURE 2, of an alternative form of fastening fixture;

FIGURE 5 shows, in plan, a spring clip used for the fixture of FIGURE 4;

FIGURE 6 shows a second alternative form of fastening fixture for use with a casing made of thermo-plastics material;

FIGURE 7 shows, in plan, a washer used in the fixture of FIGURE 6;

FIGURE 8 is a side view of a potentiometer casing held together by fixtures in accordance with a further embodiment of the invention and showing the position of a hot bit in broken outline;

FIGURE 9 is a section through part of the wall of the casing taken on the line indicated by the arrows VIII- VIII in FIGURE 8; and,

FIGURE 10 shows a stage in the manufacture of the casing of FIGURE 8.

Referring to FIGURE 1 a casing 1 is formed by two part-casings 2, 3 which fit together along a common division line 4. The casing is of parallelepiped shape and is provided at one end with a slotted head 5 rotatable to vary the setting of an electrical potentiometer the components of which are mounted inside the casing. The construction of the potentiometer may be of any of the forms well-known in the art and will not therefore be described. Terminals (not shown) extend from the underside of part-casing 2 and enable electrical connections to be made to the slider and the two ends of the potentiometer.

Each part-casing is provided on each of its longer sides with two projections 6. Only two of the projections 6 are shown in FIGURE 1 but it will be understood that the two disposed on the opposite side of each part-casing are arranged diametrically opposite and are identical to the projections shown. The projections 6 are integrally moulded with the associated part-casing from thermoplastics material and each projection is of semi-cylindrical cross section. As is clearly shown in FIGURE 1 the projections 6 of part-casing 3 are disposed directly opposite the projections 6 of the part casing 2 and the diametric surface of each projection 6 is coplanar with the division line 4.

Referring now to FIGURE 2 it will be seen that the part-casings 2, 3 fit together with a spigot and socket connection 7. The corner edges of the projections 6 are bevelled at 8 to provide a smooth lead-on for a grip washer 9 made of spring steel. Washer 9 is shown in more detail in FIGURE 3 from which it will be seen to have four inwardly directed teeth 10 presenting sharp edges which bite into the projections 6 when the washer is sprung onto the opposed projections, as shown in FIGURE 2. It will be seen that the teeth 10 are inclined slightly away from the plane of the washer on the side remote from the casing so that any attempt to remove the washer 9, except by means of a special tool, will result in the teeth 10 biting more firmly into the cylindrical wall provided by the two projections 6 so that dislodgement of the washer 9 is prevented. The washer 9 therefore serves as a locking element which hold the two projections 6 rigidly in relative positions.

FIGURES 4 and 5 show another embodiment of the invention. Here, the parts corresponding to those shown in FIGURE 2 are similarly referenced but are provided with an index dash. In FIGURE 4 the fixture comprises two projections 6' each of semi-cylindrical cross section and integrally formed with respective part-casings 2' and 3' by a moulding operation using a thermo-setting plastics material. In the embodiment of FIGURE 4 the two projections 6 are held together by an arcuate E-clip 11 made of spring steel and shown more clearly in FIGURE 5. The E-clip is provided with three inwardly directed teeth 12 which bite into the floor of a shallow annular channel 13 formed adjacent the side of the casing around the root portions of the projections 6'. The E-clip 11 is so arranged that it can be snapped into the channel 13 so that it embraces slightly more than half of the root portions of the two projections 6. It will be appreciated that the E-clip will securely hold the two part-casings 2, 3' together as long as it is in position in the channel but it may be readily removed from the channel by a suitable tool to allow the two part-casings to be separated from one another so that the components of the potentiometer inside the casing can be inspected and replaced if necessary. The potentiometer can then be reassembled and the E-clip replaced to lock the two part-casings together.

FIGURES 6 and 7 show a fixture in accordance with a third embodiment of the invention and used to secure together two part-casings 2", 3" moulded from thermoplastics material. During the moulding stage each part-casingis integrally formed with two semi-cylindrical projections 16 (shown in broken outline in FIGURE 6) arranged in similar manner to the projections 6 of FIGURE 1. The two projections 16 together provide a cylinder over which is slid a thin metal washer or ring 17 shown in FIGURE 6. Heat and pressure are then applied to the projecting end-portion of the cylinder so that it is deformed into a rivet-like shape 18 which retains the washer 17 in position. It will thus be appreciated that the two part-casings 2", 3" are held to one another by the combined strength of the metal washers 17 which are firmly locked in position against the side of the casing by the expanded terminal portions 18 of the semi-cylindrical projections 16.

Turning now to FIGURE 8 this shows two part-casings 20, 21 made of thermo-plastics material and fastened to one another by two flat metal plates 22 lying respectively against opposite longer sides of the casing. The two partcasings together form the casing of a potentiometer having a .slotted head 23 accessible at one end of the casing to vary the setting of the potentiometer. The part-casing 20 is provided with three terminals 24, 25 and 26 which enable external electrical connections to be made respectively to the two ends of the potentiometer resistor (not shown) and the potentiometer slider (not shown) which is movable by the slotted head 23 lengthwise of the resistor.

The plate 22 is made of brass and is provided with six openings 27 arranged in two groups of three and containing respective studs 28 shaped as shown in FIGURE 9. These studs 28 are provided with peripheral flanges 29 which are of larger diameter than the openings 27 in the plate 22 and therefore holds the plate securely against the coplanar sides of the two part-casings 20, 21 respectively.

The method of forming the studs 28 is shown in FIG- URE 10. The studs are shaped from projections 30 of truncated pyramidal shape and disposed opposite the positions of the openings 27. Each of the openings in the plate 22 is of frusto-conical shape and the diameter of the extremity of the projection 30 is equal to the minimum diameter of the opening 27. This enables the plate 22 to be applied over the ends of the projections 30 after the two part-casings 20, 21 have been fitted together, although the diameter of the root portions of the projections 30 prevents the plate 22 from lying fiat against the sides of the part-casings 20, 21.

The metal plate 22 has good thermo-conducting properties and, when in position over the projections 30 as shown in FIGURES 8 and 10, a hot-bit 31 is applied to it to heat the plate along its length. The heat and pressure of the bit 31 are transmitted through the plate 22 to the root portions of the projections 30 and causes them to melt around their peripheries so that the thermo-plastics material of all of the root portions flows through the openings 27 and forms the peripheral flanges 29 shown in FIG- URE 8. Each flange 29 overlaps the marginal portion of the plate 22 around the opening 27 so that when the applied pressure has forced the plate 22 to the position shown in FIGURE 9 and the bit 31 is removed, the plate 22 is held firmly against the side of the casing by the flanges 29 formed around each of the projections 28. It will be appreciated that various modifications of the arrangement shown in FIGURES 8 to 10 are possible. For example, by suitably shaping the hot-bit and applying it to the plate 22 around each of the openings 27 in turn, the deformation of the protruding portion of projection 28 may be made to assume any desired shape.

The arrangement shown in FIGURES 8 to 10 may also be used to fasten together a stack of part-casings arranged side-by-side as is used in some plug-and-socket connectors. In this case the stack is assembled and two metal plates provided with apertures registering with projections on the part-casings are placed against opposite sides of the stack. Heat and pressure are then applied to the two plates to force them against the sides of the stack While simultaneously deforming the projections into headed studs as described in FIGURES 8 to 10.

Similarly, a stack of part-casings arranged side-by-side may be fastened together by a modification of the arrangement shown in FIGURES 1 to 3. In this case the stack is assembled and two metal plates provided with apertures registering with projections on the part-casings are placed against opposite sides of the stack. The apertures may have stellated or castellated edges to provide them with teeth which are directed inwardly and slope away from the side of the casing. The two plates are forced towards the sides of the casing so that the projections are pushed through the toothed holes until the plates rest against the sides of the casing. The part-casings are thus held rigidly together by the plates which are themselves held in position by the teeth biting into the projections of the partcasings.

The forms of the invention here described and illustrated are presented merely as examples of how the invention may be embodied and applied. Other forms, embodiments and applications of the invention, coming within the proper scope of the appended claims, will of course suggest themselves to those skilled in the art.

I claim:

1. A component casing of parallelepiped shape formed by two part-casings moulded of plastics material and fitting together along a common division line, and fixtures projecting from opposite sides of said casing in the region of said division line holding said part-casings together; each fixture comprising two part-cylindrical projections extending from. respective part-casings and having their root portions formed with necks, said projections having contiguous planar surfaces clamped together by a locking element formed by a toothed metal E-clip, said E-clip being sprung over to clasp said two projections tightly together.

2. A component casing of parallelepiped shape formed by two part-casings moulded of plastics material and fitting together along a common division line, and fixtures projecting from opposite sides of said casing in the region of said division line holding said part-casings together; each said fixture comprising two part-cylindrical projections extending from respective part-casings with their free ends bevelled and having contiguous planar surfaces, and a locking element formed by an internally toothed washer having its teeth inclined away from the side of said casing and sprung over said two projections so as to clasp them tightly together.

3. A component casing having two moulded part-casings fitting together along a common division line and fixtures projecting from opposite sides of said casing holding said part'casings together, each of said fixtures comprising two projections integral with respective part-casings and a locking element comprising an apertured plate through which said projections pass, said projections being provided with enlarged heads to hold said apertured plate against the side of said casing.

4. A component casing having two moulded part-casings fitting together along a common division line and fixtures projecting from opposite sides of said casing holding said part-casings together, each of said fixtures comprising two projections integral with respective part-casings and a locking element comprising a ring through which said projections pass, said projections being provided with enlarged heads to hold said ring against the side of said casing.

5. A component casing as set forth in claim 4, in which said two projections are each of semi-circular cross-section and have their diametric faces coplanar with said division line and lying opposite one another, said enlarged heads extending radially beyond the periphery of said ring.

6. A component casing having two moulded part-casings fitted together along a common division line and fixtures projecting from opposite sides of said casing holding said part-casings together, each of said fixtures comprising two projections integral with respective part-casings and a locking element through which said two projections pass and which is held by them against the side of said casing, said locking element comprising a metal plate hav ing toothed apertures through which respective projections pass, the teeth of said apertures biting into the material of said projections to hold said apertured plate firmly against the side of said casing.

References Cited UNITED STATES PATENTS 1,238,885 9/1917 Chmela 174-92 FOREIGN PATENTS 1,153,020 2/1958 France.

JOSEPH R. LECLAIR, Primary Examiner. JAMES B. MARBERT, Examiner. 

1. A COMPONENT CASING OF PARALLELEPIPED SHAPE FORMED BY TWO PART-CASINGS MOULDED OF PLASTICS MATERIAL AND FITTING TOGETHER ALONG A COMMON DIVISION LINE, AND FIXTURES PROJECTING FROM OPPOSITE SIDES OF SAID CASING IN THE REGION OF SAID DIVISION LINE HOLDING SAID PART-CASINGS TOGETHER; EACH FIXTURE COMPRISING TWO PART-CYLINDRICAL PROJECTIONS EXTENDING FROM RESPECTIVE PART-CASINGS AND HAVING THEIR ROOT PORTIONS FORMED WITH NECKS, SAID PROJECTIONS HAVING CONTIGUOUS PLANAR SURFACES CLAMPED TOGETHER BY A LOCKING ELEMENT FORMED BY A TOOTHED METAL E-CLIP, SAID E-CLIP BEING SPRUNG OVER TO CLASP SAID TWO PROJECTIONS TIGHTLY TOGETHER. 